Polymer/layered silicate nanocomposites: a review from preparation to processing

This review is designed to be a comprehensive source for polymer nanocomposite research, including fundamental structure/property relationships, manufacturing techniques, and applications of polymer nanocomposite materials. In addition to presenting the scientific framework for the advances in polymer nanocomposite research, this review focuses on the scientific principles and mechanisms in relation to the methods of processing and manufacturing with a discussion on commercial applications and health/safety concerns (a critical issue for production and scale-up). Hence, this review offers a comprehensive discussion on technology, modeling, characterization, processing, manufacturing, applications, and health/safety concerns for polymer nanocomposites.

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Review article: Polymer-matrix Nanocomposites, Processing, Manufacturing, and Application: An Overview

Recycling and recovery routes of plastic solid waste (PSW): A review

In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.

Applications of nanotechnology in food packaging and food safety: Barrier materials, antimicrobials and sensors

A review of vapor grown carbon nanofiber/polymer conductive composites

The differential scanning calorimeter (Perkin-Elmer DSC-1) is used to characterize the cure of a general-purpose polyester during isothermal and scanning experiments. The technique is based on a new proposed model for the kinetics of isothermal cure. The model yields results which are in good agreement with experimental isothermal rate of reaction and integral heat of reaction data. It also gives some information about the residual reactivity of the sample after an isothermal cure experiment. With the aid of the proposed kinetic model, it is possible to obtain integral heats of reaction and rates of heat generation at different temperatures during a scanning experiment. The difference between the rate of heat input to the sample and the heat of reaction at any instant during scanning may be used to calculate the specific heat of the sample at the same instant. Specific heat data show two maxima during each scanning experiment. These maxima may be associated with transitions occurring during cure in the melt and rubbery states.

Kinetics and thermal characterization of thermoset cure

Mechanical and barrier properties of nanocrystalline cellulose reinforced chitosan based nanocomposite films.

The modeling of the electrical conductivity of polymer composites reinforced with conductive fibers is investigated. Existing models generally can be divided into percolation theories and non-percolation theories. The basis of the percolation theory is the fact that the conductivity of the composite increases dramatically at a certain fiber concentration called the percolation threshold. This theory can be used to model the behavior of the composite or to predict the percolation threshold itself. Non-percolation theories include terms, which account for microstructural data such as fiber orientation, length, and packing arrangement. A comparison of experimental data with predictions from the various models reveals that only the percolation theory is able to accurately model the conductive behavior of an actual composite. Two alternative new models, which predict the volume resistivity of a composite using microstructural data, are evaluated. The first model relates resistivity to the concentration and orientation of the fibers, while assuming perfect fiber-fiber contact. The relationship between resistivity and fiber concentration predicted by the model is in qualitative agreement with actual data, and predictions of the anisotropy in volume resistivity compare well with experimental results. The second model accounts for the effect of fiber-fiber contact and fiber length on composite resistivity. Predictions are in excellent agreement with experimental data for polypropylene composites reinforced with nickel-coated graphite fibers.

Estimation of the volume resistivity of electrically conductive composites

The hydrolytic depolymerization of molten PET in excess water was studied using a 2 L stirred pressure reactor at temperatures of 250, 265, and 280°C. Rate constants for hydrolysis are calculated from the initial rate data. At initial water: PET charge ratios (w/w) exceeding 5.1, essentially complete depolymerization to monomer is possible at 265°C. At lower water: PET initial charges, an equilibrium is established. The equilibrium constants are calculated for 2 g water/g PET at three temperatures. A kinetic model is proposed to describe the hydrolysis reaction. The model is shown to fit experimental data and to yield good predictions for the equilibrium concentration of carboxyl groups. Carboxyl-group concentrations are measured using an end-group analysis technique. Potentiometric titrations are carried out in one of two solvent systems, dimethylphenol:chloroform or dimethylsulfoxide, depending on the extent of hydrolysis. © 1993 John Wiley & Sons, Inc.

A kinetic study of the hydrolytic degradation of polyethylene terephthalate at high temperatures

A mathematical model is proposed for the quantitative treatment of the injection molding of thermoplastics as it relates to the behavior of polymer in the cavity. The model is based on setting up the equations of continuity, motion, and energy for the system during each of the stages of the injection molding cycle (filling, packing and cooling) and the coupling of these equations with practical boundary conditions. The treatment takes into consideration the non-Newtonian behavior of the melt, the effect of temperature on density and viscosity, the latent heat of solidification, and the differences in thermal properties between the solid and the melt. In employing the model, it is necessary to know the pressure-time variation at the cavity entrance. Numerical solutions have been obtained for the case of spreading radial flow in a semi-circular cavity. The numerical results yield significant data on the progression of the melt front, the flow rate, and the velocity profiles at different times and positions in the cavity. They also yield temperature and pressure profiles throughout the packing and cooling stages.

Musa R. Kamal

Papers

Kinetics and thermal characterization of thermoset cure

Mechanical and barrier properties of nanocrystalline cellulose reinforced chitosan based nanocomposite films.

Estimation of the volume resistivity of electrically conductive composites

A kinetic study of the hydrolytic degradation of polyethylene terephthalate at high temperatures

The injection molding of thermoplastics part I: Theoretical model